| Molecular reaction dynamics studies the microcosmic dynamics and principle of the chemical reaction on atomic and molecular level. It can elucidate not only structures, characters and functions of all kinds of transient species during reaction, but also intrinsic law of chemical reaction from the research on state-to-state reaction dynamics and the interaction of coherent states. The wave packet dynamics is an important branch of physical chemistry. The time-dependent wave-packet method is good for the excitation and ionization of molecule in the strong laser field. Besides its numerical efficiency, time-dependent wave-packet method is conceptually simple. It provides not only a classical-like interpretation, but also the quantum precision. The time-dependent wave-packet method is especially applicable to the system which evolutes with time.Recently, in the theoretical research fields of photoionization dynamical behavior, much attention is focused on small molecules. In the theoretical treatment of single molecule dynamics, one spatial dimension and two-state system is the simplest one. The introduction of the appropriate computational approaches to the dynamics of wave-packets on this system is very important for understanding the treatment of complex systems. Besides, it has theoretical and practical instruction for chemical reaction controlling. The treatment about small molecules'multi-photon ionization not only use for reference about the big molecules'action in intense external field, but also have theoretical and practical significance to understand or carry the laser control on atom and molecule.Scince P. Johnson applied multiphoton ionization technique to the molecule system, molecular resonance enhanced multiphoton ionization (REMPI) has been achieved. This technique is an effective tool for studying electronic excited states including radiation states without fluorescence. The resenance enhanced multiphoton ionization photoelectron energy spectroscopy of the molecules can provide informations about intermediate excited states. It's best excellence is that all of the electronic excited states ionized by laser can be studied. The technique of resenance enhanced multiphoton ionization photoelectron energy spectroscopy is a useful one for study excitated states of small molecules. In this paper SH radical (2+1) multiphoton ionization photoelectron energy spectroscopy were studied by the split-operator technique of time-dependent wave-packet method in quantum mechanics. The main work is given as follows:(1) The fundamental theory of wave-packet dynamics associated with our work is introduced. This starts by giving the basic concept of wave-packet and its application to dynamics. Then take the diatomic molecule as an example, how the time-dependent Schr?dinger equation with the proper Hamiltonian is solved for the system is shown. The numerical tools used for solving the wave-packet dynamics from a coupled Schr?dinger equation are also provided.(2) The basic theory of the excited-state molecular photo-ionization dynamics is presented. A survey of work using resonance-enhanced multi-photon ionization and double-resonance to study excited-state photo-ionization dynamics in molecules is reviewed. The theoretical method to deal with the transition moment is briefly given in the theoretical background. This treatment of photo-ionization processes can be used as a basis for understanding excited-state photo-ionization. As a major investigation object through out our work, the technique of MPI TRPES is introduced. Its characteristics, its differences with the spectrum of multiphoton ionization, as well as its application to molecular dynamics are also discussed.(3) The wave-packet is propagated using the"split operator-Fourier transform"method. The time-resolved photoelectron spectrum of SH radical 2+1 multi-photon ionization is simulated using the time-dependent wave-packet method. The calculated results show that the change of delay time and laser intensity will influence the photoelectron spectrum. The intensity of spectrum can be controlled by altering the parameters of the laser pulses, the number and the position of peak will also be effected.This submitted work is divided into four chapters. The first chapter is the introduction, which briefly discusses the basic theory of molecular reaction dynamics. Also the development of the wave-packet dynamics is presented. Chapter two introduces the major theory of wave-packet dynamics. In chapter three introduces the conception of the spectrum of photoelectron and the technique of resonance enhanced multiphoton ionization. In chapter four, the 2+1 multiphoton ionization photoelectron energy spectroscopy of SH radical is given. The"split operator-Fourier transform"method of time-dependent wave packet propagation is employed to reproduce the experimental obtained MPI PES of SH radical in different pump-probe delay time and different intensity of laser. |
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